Mr Reckless said he had not taken the decision lightly but said the Conservative leadership was "part of the problem that is holding our country back".

"These decisions are never easy. Mine certainly hasn’t been. Many have been the sleepless nights when I have talked it over with my wife and thought about the future of our children.

"These decisions are never easy and this certainly has not been. It is a decision I make from optimism. Born from belief that Britain can be better and of my knowledge of how the Westminster parties hold us back and my belief of the fresh start UKIP offers.

"We all know the problem of British politics. People feel disconnected. Disconnected is too mild a word. People feel ignored. Taken for granted. Over taxed. Over regulated. Ripped off and lied to.

"They have reason to. With some honourable exceptions MPs are not local representatives but agents of a political class.

"Instead of championing their constituents interests, too often they champion their parties interests in their constituencies.

"I remember the promises I made to my constituents in Rochester and STrood, and I intend to keep them. I promised we would cut immigration, cut the deficit so we could reduce taxes, decentralise power and promised we would have a more open and accountable politics.

Rochester and Strood MP Mark Reckless

"And above all, I promised we would get our country out of the European Union.

"Shall I tell you something? I have found it is impossible to keep those promises as a Conservative and that's why I'm joining UKIP."

He continued: "If you vote UKIP, you get UKIP. I promise a straight in or out referendum.

"I can't promise that as a Conservative, but I can as UKIP. I want to make the case for British independence," Mr Reckless said.

@MarkReckless was an impressive voice in parliament and a good MP. I fear he has condemned himself to irrelevance. Rochester is not Clacton

Andrew Mackness, chairman of Rochester and Strood Conservatives, said: "I am astonished and disgusted by Mark Reckless' decision - only 48 hours ago he proclaimed his support for the Conservatives and their plans for a referendum on Europe and he gave me assurances he wouldn’t defect.

Andrew Mackness

He has misled the hardworking people of Rochester and Strood who voted for him."

Mark Hanson, the UKIP Prospective Parliamentary Candidate for Rochester and Strood has stepped aside to allow Mr Reckless to stand.

Labour Parliamentary Candidate for Rochester & Strood Naushabah Khan said: "With such division in the Medway Tory party, it's clear that there is only one choice in Medway for the progressive, fair vote and that is Labour.

Naushabah Khan Labour Parliamentary Candidate for Rochester & Strood

"We have a 10 year plan to save the NHS, including the extra resource of 20,000 more nurses, 8,000 more GPs and 5,000 more careworkers.

"In Rochester and Strood, we have a choice between a Labour party that will save the NHS or a Tory party that is in a race with UKIP to the far-right."

Labour group leader Vince Maple

Vince Maple, Leader of Medway Labour Group, said: "Today's news just confirms what we suspected about the MP for Rochester and Strood.

"His switch from the Tories to UKIP reveals the divisions in the Medway Conservative party.

"On the eve of his conference we again see that Conservatives' confidence in Cameron is plummeting. David Cameron has always pandered to his right, and even now they are deserting him.

"This also underlines that UKIP are a party of Tory people, Tory policies and Tory money.

"It is clearer than ever that only Labour has a plan to make everyday working people across the country better off."

KM Group Political Editor Paul Francis assesses the impact of Mark Reckless' defection to Europe:

No wonder Nigel Farage has a smile as wide as a Cheshire cat.

After stunning the Conservatives with the news that Douglas Carswell was defecting to UKIP comes another bombshell - the defection of Rochester and Strood MP Mark Reckless.

It was detonated with the aim of maximising the Conservatives' discomfort, coming on the eve of their party conference and threatening to overshadow it by thrusting Europe centre stage at a time when the Conservatives would prefer to be focusing on other issues.

There has been a hostile reaction from the Conservatives, who have accused him of betraying his voters and his party. Fellow Medway MP Tracey Crouch , fizzing with indignation, said he had told her directly defection was not in mind and felt "angry and let down".

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UKIP leader Nigel Farage, on the other hand, said his defection was "very, very principled indeed."

Some will certainly regard this as a betrayal - especially given his public denials that he had no intention of quitting the Conservatives up until fairly recently.

It s not entirely clear when he decided to jump ship but it is hard to believe that he woke up one day last week and concluded the time was right.

The issue now is whether, once UKIP's euphoria has subsided and the dust has settled, he can pull off a coup and win a by-election in a seat where he has a majority nudging 10,000.

In his favour is that the Conservatives, who have been stunned by the news, will need to find a candidate swiftly and will not have been prepared to get into campaigning mode just yet.

Labour, too, will have been caught on the hop but at least they have a candidate and can probably mobilise their activists and supporters quickly to get on to the front foot .

If UKIP win in Clacton next month, then it will have a momentum that could be hard to stop.

The by-election is bound to be dominated by Europe much as the other parties will want it to be about a range of issues.

Would you bet against Mark Reckless pulling off a sensational win? Possibly not.And if he does, David Cameron could find his own position decidedly uncomfortable.